Reed Richards says that Superman is perhaps the most powerful hero on both earths and Thor is explicitly name dropped by Franklin Richards as well.

There are other indirect comparisons as well but I think that puts Superman ahead of Thor in their encounters by quite a bit.

Thoughts?

but we also know that Thor has fought Glads evenly more than once, and that the Eric/Thor was able to stalemate Gladiator in a direct test of strength.

Here are a few things we know for sure:

Superman defeated Professor Hulk, whom many consider less impressive than Savage, and I think almost anyone would consider less impressive than Gravage. This was also fan voted.

Superman stalemated the Gravage Hulk in the later Roger Stern crossover.

Pre Crisis Superman kind of beat the Hulk, but as Hulk was getting angrier and stronger, the text indicated that Hulk might well surpass Superman, and this is Pre Crisis Superman.

Superman has repeatedly been shown as equal to Captain marvel/Shazam, and a peer to Black Adam...and this has been in pre crisis crossovers, post crisis, animated, whatever. Action comics 768 goes out of its way to affirm this, when Superman gets the power of Captain Marvel and at the end professes that he considers Marvel his equal in every way

Thor convincingly defeated Captain Marvel in a non voted crossover

We also know that DC Thor lost once to Big Barda (but then so did Superman), and also died fighting alongside WW and Superman in a 1000 year war, but seemed to be peers (and Superman weilded his Mjolnir after his death).

We know that Supreme was able to kill Thor after a good fight, and weild Mjolnir

We know that Thor can and has stalemated or beaten Superman knockoffs like Hyperion and Gladiator, but the results are mixed.

We know that Thor has repeatedly stalemated the Hulk versions Superman has fought

We know that both tend to hold back and don't use their versatility particularly effectively either, though Thor's holding back seems to be subconscious a lot of the time.

All in all, the way they're most likely to fight, I think Superman is probably a slight favorite. That said, I actually think Thor is overall more powerful (his storm, energy absorption, and other Mjolnir type powers make the difference), but in a direct, straightforward way, I think Supes would be a very slight favorite.